1. Field of the Invention
The present invention relates generally to vibratory finishing and, more particularly, to an unloading system for discharging workpieces from a bowl-type vibratory finishing machine.
2. Prior Art
Unloading systems have been proposed for use with bowl-type vibratory finishing machines. Many of these proposals call for the use of a removably positioned ramp to direct a mixture of finishing media and workpieces onto a screen which overlies the bowl. The screen effects separation of the finishing media from the workpieces. As the workpieces travel across the screen for discharge, the media drops through the screen back into the bowl.
Difficulties have been encountered with previous unloading system proposals in inserting ramps into and removing ramps from a loaded bowl. During machine operation, the mixture of workpieces and finishing media in the bowl is churning and precessing in a predetermined direction. The mass of this mixture and the forces generated during its movement tend to inhibit ramp insertion and removal. While proposals have been made to provide pivotal systems for positioning the ramp, such systems require that a relatively rigid, planar ramp structure be forced down into a moving mixture during insertion, and require that the ramp structure be forced upwardly out of the moving mixture during removal. In most instances, the forces required to effect insertion and/or removal of the ramp are significantly greater than is desired, and the operations of inserting and removing the ramp are awkward and difficult to carry out.
As is known in the art, it is oftentimes desirable to form at least one of the side walls of a finishing machine bowl such that it tapers to provide a bowl cross section which narrows in width near the top of the bowl. Such a tapering of one or both of the side walls operates, in many instances, to enhance the type of churning movement which is imparted to the mixture of finishing media and workpieces. A problem which has been encountered with proposed unloading systems is that their removable ramps are of rigid construction and are difficult, if not impossible, to insert in bowls having tapered cross sections which narrow toward the top of the bowls. This problem has caused some manufacturers to utilize bowls having side walls which do not taper but rather extend substantially vertically, thereby losing the benefit which obtains from providing bowl side walls with a tapered configuration.